This disclosure relates to a fixing device used in an image forming apparatus such as a copier, a printer, a facsimile, or a composite machine including them, and the image forming apparatus provided with such a fixing device. This disclosure more specifically relates to a technology of preventing ultra particles generated inside the fixing device from diffusing to outside of the fixing device.
In an image forming apparatus adopting an electrophotographic method, a toner is provided to an electrostatic latent image formed on a photo conductor to form a toner image, the toner image is transferred onto paper, and then the toner image on the paper is fixed by a fixing device.
In a fixing device of a heating type that heats paper to thereby fix a toner image onto the paper, ultrafine particles (UFP) generated due to the aforementioned heating may diffuse inside the image forming apparatus. In recent years, in response to a rise in the awareness of environmental problems, there have been demands for suppressing diffusion of the ultrafine particles (UFP) to outside of the apparatus. The ultrafine particles (UFP) refer to, of suspended particulate matters (SPM), particles with a diameter of 100 nm or below. It has been found that the ultrafine particles (UFP) are generated mainly from silicon rubber used as an elastic layer of, for example, a heat roller. That is, as a result of heating of the silicon rubber, low-molecular siloxane is generated and this low-molecular siloxane is diffused as ultrafine particles (UFP).
Thus, technologies of removing the ultrafine particles (UFP) are known. For example, there is a fixing device provided with an ultrafine particles remover having an absorbing fan, a dust collecting filter, and a duct. After an air flow flows through the duct from vicinity of a side surface of a fixing roller by the absorbing fan, it is discharged to outside of the image forming apparatus via the dust collecting filter, but the ultrafine particles (UFP) generated from the heat roller having the elastic layer of the silicon rubber flow through the duct together with the air flow by the absorbing fan, and are captured by the dust collecting filter. As a result, the ultrafine particles (UFP) are never discharged to the outside of the image forming apparatus.
It has been found that the ultrafine particles (UFP) are generated from not only the silicon rubber used for an elastic layer of the heat roller or a pressure roller but also a heat absorption unit formed on an inner circumferential surface of the heat roller. For example, in order to efficiently absorb heat of a heat source and transmit it to the heat roller, for the heat absorption unit, a black paint such as Celmo black, Okitomo Paint, or Tetzsol (all of which are product names) is used. These black paints are generated by adding modified silicon to metal oxide. An increase in a temperature of the heat absorption unit by the heat source raises a problem that siloxane is generated from the modified silicon of the heat absorption unit and this siloxane diffuses as ultrafine particles (UFP).